Wire passing from a supply source to a utilization device is often required to be tension controlled to prevent overrunning and subsequent tangling and snagging. Numerous wire tensioning and control devices have been developed to overcome these problems. In some instances, magnetic brakes are utilized wherein the effective strength of the magnetic field is altered in response to the operation of a wire tension sensing device.
An example of one such magnetically controlled wire tensioning device is disclosed in U.S. Pat. No. 3,072,361 issued Jan. 8, 1963, to R. E. Fuller. In this patent, wire is passed through an eyelet mounted on a tension response arm. Movement of the arm in response to changes in tension is utilized to move a pair of U-shaped permanent magnets toward or away from a disc constructed of non-magnetic metal. The disc is coupled to a sheave about which the wire is wrapped in one or more turns. Movements of the magnets in response to wire tension changes accordingly increases or decreases the distance that the magnets are positioned with respect to the disc. As the magnets move, the magnetic fields vary in strength and thus accordingly control the drag placed on the disc and the sheave to control the drag tension placed on the wire passing around the sheave.
There is still a need for a simple magnetic wire tension control device using a minimum number of easily manufactured parts. Such a device should be adapted to permit manual or automatic adjustment to control a wire passing from supply source, such as a reel, to a utilization device, such as a winding head. Further, it would be desirable if the wire tension device could be readily expanded to accommodate the control of a number of wires.